1. Field
Embodiments may relate to a lighting device, more particularly, to a lighting device including light emitting units configured of a plurality of light emitting diodes connected in series and a method of controlling a light emitted from the lighting device not to have an increasing light velocity abnormally or a reversed light velocity, during a dimming process.
2. Background
In the lighting industry, studies and researches have been still under development on a lighting source, a light emission type and a driving method of a lighting apparatus.
A conventional lighting system generally uses a lighting source such as an incandescent lamp, an electric discharge lamp and a fluorescent lamp for a household, landscape and industrial usage. Here, a resistive lighting source including the incandescent lamp has a low efficiency and a heat generation problem. The electric discharge lamp has problems of a high price and a high voltage. The fluorescent lamp has an environmental disadvantage of mercury usage.
To overcome disadvantages of those lighting sources, there have been increasing interests in a light emitting diode (LED) having advantages of light-emitting efficiency, color variety and design autonomy. There have been increasing studies and researches on a lighting system including the LED as lighting source. The LED is a semiconductor element which emits a light when a voltage is applied thereto forwardly. The LED has a long usage life, low power consumption, with electrical, optical and physical properties which are proper to mass production and the LED has been rapidly replacing the incandescent lamps and fluorescent lamps.
In the meanwhile, lighting apparatuses such as a large amount of light emitting diodes or sensors are required in a building and a plant requires a large building such as. Also, a lighting system for managing and controlling such lighting apparatuses is required.